#encoding: utf-8
'Support subclassing c++ objects in python, with some limitations. Useful primarily for pure-python preprocessors.'

from woo.core import *
from minieigen import *


class PyAttrTrait(object):
    '''
    Class mimicking the `AttrTrait` template in c++, to be used when deriving from :obj:`PyWooObject`, like in this example (can be found in `woo.pyderived` module's source)::

        class _SamplePyDerivedPreprocessor(woo.core.Preprocessor,PyWooObject):
            'Sample preprocessor written in pure python'
            _attrTraits=[
                PyAttrTrait(bool,'switch',True,"Some bool switch, starting group",startGroup='General'),
                PyAttrTrait(int,'a',2,"Integer argument in python"),
                PyAttrTrait(str,'b','whatever',"String argument in python"),
                PyAttrTrait([Node,],'c',[],"List of nodes in python"),
                PyAttrTrait(float,'d',.5,"Parameter with range",range=Vector2(0,.7),startGroup='Advanced'),
                PyAttrTrait(int,'choice',2,"Param with choice",choice=[(0,'choice0'),(1,'choice1'),(2,'choice2')]),
                PyAttrTrait(int,'flags',1,"Param with bits",bits=['bit0','bit1','bit2','bit3','bit4'],buttons=(['Clear flags','self.flags=0','Set flags to zero'],True)),
                PyAttrTrait(int,'choice2',2,'Param with unnamed choice',choice=[0,1,2,3,4,5,6,-1]),
                PyAttrTrait(Vector3,'color',Vector3(.2,.2,.2),"Color parameter",rgbColor=True),
                PyAttrTrait(float,'length',1.5e-3,"Length",unit='mm'),
            ]
            # this is needed for new-style pickling with pybind11
            def __new__(klass,**kw):
                self=super().__new__(klass)
                # do not use self.__class__ here, it would break classes derived further from this class
                self.wooPyInit(SamplePyDerivedPreprocessor,woo.core.Preprocessor,**kw)
                return self
            # this is needed for old-style pickling with boost::python
            def __init__(self,**kw):
                woo.core.Preprocessor.__init__(self)
                self.wooPyInit(SamplePyDerivedPreprocessor,woo.core.Preprocessor,**kw) 
            def __call__(self):
                pass
                # ...

    This class will be represented like this in the GUI:

    .. image:: fig/pyderived-gui.png


    :param pyType: python type object; can be

        * primitive type (like `bool`, `float`, `Vector3`, `str`, …)
        * sequence of primitive types, written as 1-list: `[bool,]`, `[float,]`, …
        * :obj:`woo Object <woo.core.Object>` or any derived type (:obj:`woo.core.Node`, :obj:`woo.dem.Sphere`, …)
        * sequence of woo objects, e.g. `[woo.core.Node,]`

        When a value is assigned to the attribute, provided type must be convertible to *pyType*, otherwise `TypeError` is raised. There are some additional restrictions:

        * `str` and `unicode` values will *not* be converted to `floats` and such − although python will accept `float('1.23')`

    :param name: name of the attribute, given as `str`
    :param ini: initial (default) value of the attribute
    :param str doc: documentation for this attribute, as it appears in generated docs and tooltips in the UI
    :param str unit: unit given as string, which is looked up in :obj:`woo.unit`; the multiplier is the ratio between *unit* and associated basic unit, which is found automatically.
        
        .. warning:: `unit` only determines multiplier for the GUI representation; it has no impact on the internal value used; in particular, the *ini* value is *unit-less*. If you want to give units to the initial value, say something like ``PyAttrTrait(float,'angle',60*woo.unit['deg'],units='deg','This is some angle')``.

    :param bool noGui: do not show this attribute in the GUI; use this for attributes which the GUI does not know how to represent (such as python objects, numpy arrays and such), to avoid warnings.
    :param bool noDump: skip this attribute when dumping/loading this object; that means that after loading (or after a :obj:`PyWooObjects.deepcopy`), the attribute will be default-initialized.
    :param bool rgbColor: this attribute is color in the RGB space (its type must be `Vector3`); the GUI will show color picker.
    :param str startGroup: start new attribute group, which is represented as collapsible blocks in the GUI.
    :param str hideIf: python expression which determines whether the GUI hide/show this attribute entry dynamically; use `self` to refer to the instance, as usual.
    :param range: give range (`Vector2` or `Vector2i`) to this numerical (`float` or `int`) attribute − a slider will be shown in the GUI.
    :param choice: this attribute chooses from predefined set of integer values; `choice` itself can be

        * list of unnamed values, e.g. `[0,1,2,3,4]` to choose from;
        * list of named values, e.g. `[(0,'choice0'),(1,'choice1'),(2,'choice2')]`, where the name will be displayed in the GUI, and the number will be assigned when the choice is made.

    :param bits: give names for bit values which this (integer) attribute which represents; they will be shown as array of checkboxes in the GUI.
    :param buttons: Tuple of *list* and *bool*; in the flat list of strings, where each consecutive triplet contains

        1. button label
        2. python expression to evaluate when the button is clicked
        3. label to be shown as button description in the GUI

        The bool at the end determined whether the button is created above (*True*) or below (*False*) the current attribute.
    
    :param filename: `str` attribute representing filename with file picker in the GUI; the file is possibly non-existent.
    :param existingFilename: `str` attribute for existing filename, with file picker in the GUI.
    :param dirname: `str` attribute for existing directory name, with directory picker in the GUI.
    :param triggerPostLoad: when this attribute is being assigned to, `self.postLoad('attrName')` will be called.

    '''
    #        
    # fake cxxType
    #
    primitiveTypes={int:'int',str:'string',float:'Real',bool:'bool',
        Vector2:'Vector2r',Vector3:'Vector3r',Vector6:'Vector6r',Matrix3:'Matrix3r',Matrix6:'Matrix6r',
        Quaternion:'Quaternionr',Vector2i:'Vector2i',Vector3i:'Vector3i',Vector6i:'Vector6i',
	AlignedBox3:'AlignedBox3r',
	MatrixX:'MatrixXr',VectorX:'VectorXr',
    }
    def __init__(self,pyType,name,ini,doc,# *,
            unit=None,
            noGui=False,
            noDump=False,
            #multiUnit=False,
            rgbColor=False,
            #prefUnit=None,
            #altUnit=None,
            startGroup=None,
            hideIf=None,
            range=None,
            choice=None,
            bits=None,
            buttons=None,
            altUnits=None,
            filename=False,
            existingFilename=False,
            dirname=False,
            psd=False,
            triggerPostLoad=False,
            guiReadonly=False,
            noGuiResize=False,
            colormap=False,
            deprecated=False
        ):
        # validity checks
        if range:
            if (pyType,type(range)) not in [(int,Vector2i),(float,Vector2)]: raise TypeError("Range must be Vector2 for floats and Vector2i for ints")
        if isinstance(pyType,list):
            if len(pyType)!=1: raise TypeError('Type must be a list of length exactly one, or a plain type')
            if pyType[0] in self.primitiveTypes: self.cxxType='vector<%s>'%self.primitiveTypes[pyType[0]]
            elif isinstance(pyType[0],type): self.cxxType='vector<shared_ptr<%s>>'%(pyType[0].__name__)
            else: raise TypeError('List element must be a type, not a %s'%(str(pyType[0])))
            # force correct types in the sequence
            if pyType[0] in self.primitiveTypes: ini=[pyType[0](i) for i in ini]
            else:
                for i,v in enumerate(ini):
                    if v==None: continue # this is OK
                    if not isinstance(v,pyType[0]): raise TypeError("%d-th initial value item must be a %s, not a %s"%(i,pyType[0],type(v)))
        elif pyType in self.primitiveTypes:
            self.cxxType=self.primitiveTypes[pyType]
            ini=pyType(ini)
        elif isinstance(pyType,type):
            self.cxxType='shared_ptr<%s>'%pyType.__name__
        else: raise ValueError('Type must be a list of length one, or a primitive type; not a %s'%str(pyType))
        #
        #
        # mandatory args
        self.pyType=pyType
        self.name=name
        self.ini=ini 
        self.doc=doc
        # optional args
        self.noGui=noGui
        self.noDump=noDump
        self.rgbColor=rgbColor
        self.startGroup=startGroup
        self.hideIf=hideIf
        self.range=range
        self.choice=choice
        self.bits=bits
        self.buttons=buttons
        self.filename=filename
        self.existingFilename=existingFilename
        self.dirname=dirname
        self.triggerPostLoad=triggerPostLoad
        self.noGuiResize=noGuiResize
        self.colormap=colormap
        self.deprecated=deprecated
        self.readonly=guiReadonly # this has different meaning in c++ and python, so call it differently
        # those are unsupported in python
        self.noSave=self.hidden=self.pyByRef=self.static=self.activeLabel=self.namedEnum=False
        #
        self.validator=None
        if self.choice and isinstance(self.choice[0],str):
            #print '%s: Choice of strings (%s)!!!!'%(self.name,str(self.choice))
            # choice from strings
            def validateStrChoice(self,val):
                if val not in self.choice: raise ValueError("%s: '%s' is not an admissible value (must be one of: %s)"%(self.name,str(val),', '.join(["'%s'"%str(c) for c in self.choice])))
            self.validator=validateStrChoice
        # PSD buttons
        if psd:
            if self.buttons: raise ValueError("%s: psd and buttons are mutually exclusive (psd created a button for displaying the PSD)"%self.name)
            self.buttons=(['Plot the PSD','import pylab; pylab.plot(*zip(*self.%s)); pylab.grid(True); pylab.show();'%(self.name),''],0)
        # side-effects of deprecated
        if self.deprecated:
            self.noGui=self.noDump=True
        # 
        # units
        #
        import woo._units
        baseUnit=woo._units.baseUnit
        def _unicodeUnit(u):
            if isinstance(u,str): return u
            elif isinstance(u,tuple): return (_unicodeUnit(u[0]),u[1])
            raise ValueError(u"Unknown unit type %sfor %s"%(str(type(u)),u))
        if isinstance(unit,str):
            unit=[_unicodeUnit(unit)]
            if altUnits: altUnits=[[_unicodeUnit(a) for a in altUnits]]
        if not unit:
            self.unit=None
            self.multiUnit=False
            self.prefUnit=None
            self.altUnits=None
        elif isinstance(unit,list) or isinstance(unit,tuple):
            self.multiUnit=(len(unit)>1)
            self.unit=[]
            self.altUnits=[]
            self.prefUnit=[]
            for u in unit:
                # print self.name,u
                if u not in baseUnit: raise ValueError(u'Unknown unit %s; admissible values are: '%u+', '.join(baseUnit.keys()))
                base=baseUnit[u]
                self.unit.append(base)
                self.prefUnit.append((u,1./woo.unit[u]))
                alts=[]
                for alt in baseUnit:
                    if baseUnit[alt]==base and alt!=base: alts.append((alt,1./woo.unit[alt]))
                self.altUnits.append(alts)
            # user-specified alternative units
            if altUnits:
                if len(altUnits)!=len(self.unit): raise ValueError("altUnits must be of the same length as unit")
                for i,au in enumerate(altUnits):
                    self.altUnits[i]+=au
        else: raise ValueError('Unknown unit type %s (must be list, tuple, str, unicode): %s'%(type(unit).__name__,str(unit)))
    def validate(self,val):
        'Called when the attribute is set'
        if self.validator: self.validator(self,val)
    def coerceValue(self,val):
        'Check whether *val* has type compatible with declared type (pyType). Raise exception if not. Values converted to required types are returned (it is safe to ignore the return value). In addition, validate the (converted) value, if a validator is defined'
        def tName(T): return (T.__module__+'.' if T.__module__!='__builtin__' else '')+T.__name__
        # sequences
        if isinstance(self.pyType,list):
            assert len(self.pyType)==1
            ret=[]
            if not hasattr(val,'__len__'):
                raise TypeError("Attribute {self.name} declared as sequence of {T}{cxxType}, but its value {val!s} of type {valType} is not a sequence (__len__ not defined).".format(self=self,T=tName(self.pyType[0]),val=val,valType=tName(type(val)),cxxType=((' ('+self.cxxT+' in c++') if hasattr(self,'cxxT') else '')))
            T=self.pyType[0]
            if T in self.primitiveTypes: # check convertibility
                for i,v in enumerate(val):
                    try:
                        if isinstance(v,str) and T in (float,int): raise TypeError("Don't allow conversions from strings to numbers, since that will fail if used without conversion")
                        ret.append(T(v))
                    except: raise TypeError("Attribute {self.name} declared as sequence of {T}, but {i}'th item {v!s} of type {itemType} is not convertible to {T}.".format(self=self,i=i,v=v,itemType=tName(type(v)),T=tName(T)))
            else:
                for i,v in enumerate(val):
                    ret.append(v)
                    if v==None: continue # python representation for NULL shared_ptr
                    if not isinstance(v,T): raise TypeError("Attribute {self.name} declared as a sequence of {T}, but {i}'th item {v!s} of type {itemType} is not a {T}.".format(self=self,i=i,v=v,itemType=tName(type(v)),T=tName(T)))
        else:
            # do the same as for sequence items; ugly code duplication
            T=self.pyType
            if T in self.primitiveTypes:
                try:
                    if isinstance(val,str) and T in (float,int): raise TypeError("Don't allow conversions from strings to numbers, since that will fail if used without conversion")
                    ret=T(val)
                except: raise TypeError("Attribute {self.name} declared as {T}, but value {val!s} of type {valType} is not convertible to {T}".format(self=self,val=val,valType=tName(type(val)),T=tName(T)))
            else:
                # objects
                ret=val
                if val!=None and not isinstance(val,T): raise TypeError("Attribute {self.name} declared as {T}, but value {val!s} of type {valType} is not a {T}".format(self=self,val=val,valType=tName(type(val)),T=tName(T)))
        self.validate(ret)
        return ret
    def __str__(self): return '<PyAttrTrait '+self.name+' @ '+str(id(self))+'>'
    def __repr__(self): return self.__str__()

class PyWooObject(object):
    '''
    Define some c++-compatibility functions for python classes. Derived class is created as::
        
        class SomeClass(woo.core.Object,woo.pyderived.PyWooObject): # order of base classes important!
            _attrTraits=[
                # see below
            ]
            # new-style pickling with pybind11
            def __new__(klass,**kw):
                self=super().__new__(klass)
                self.wooPyInit(SomeClass,woo.core.Object,**kw)
                return self
            # for old-style pickling with boost::python
            def __init__(self,**kw):
                woo.core.Object.__init__(self)
                self.wooPyInit(SomeClass,woo.core.Object,**kw)   # do NOT use self.__class__ instead of SomeClass, that would break classes deriving from SomeClass

    This new class automatically obtains several features:

    * dumping/loading via :obj:`woo.core.Object.dump` etc works.
    * the GUI (:obj:`woo.qt.ObjectEditor`) will know how to present this class.
    * documentation for this class will be generated
    * all attributes are type-checked when assigned
    * support for postLoad hooks (see below)

    The `_attrTraits` ist a list of :obj:`PyAttrTrait`; each attribute
    is defined via its traits, which declare its type, default value, documentation and so on -- this
    is documented with :obj:`PyAttrTrait`.

    This example shows trait definitions, and also the `triggerPostLoad` flag::

        class SomeClass(woo.core.Object,woo.pyderived.PyWooObject):
            _PAT=woo.pyderived.PyAttrTrait # alias for class name, to save typing
            _attrTraits=[
                _PAT(float,'aF',1.,'float attr'),
                _PAT([float,],'aFF',[0.,1.,2.],'list of floats attr'),
                _PAT(Vector2,'aV2',(0.,1.),'vector2 attr'),
                _PAT([Vector2,],'aVV2',[(0.,0.),(1.,1.)],'list of vector2 attr'),
                _PAT(woo.core.Node,'aNode',woo.core.Node(pos=(1,1,1)),'node attr'),
                _PAT([woo.core.Node,],'aNNode',[woo.core.Node(pos=(1,1,1)),woo.core.Node(pos=(2,2,2))],'List of nodes'),
                _PAT(float,'aF_trigger',1.,triggerPostLoad=True,doc='Float triggering postLoad'),
            ]
            def postLoad(self,I):
                if I==None: pass                  # called when constructed/loaded
                elif I=='aF_trigger': pass # called when aF_trigger is modified
            def __new__(klass,**kw):
                pass
                # ...
            def __init__(self,**kw):
                pass
                # ...

    The `postLoad` function is called with
    
    * `None` when the instance has just been created (or loaded); it *shoud* be idempotent, i.e. calling `postLoad(None)` the second time should have no effect::

        SomeClass()         # default-constructed; will call postLoad(None)
        SomeClass(aF=3.)    # default-construct, assign, call postLoad(None)

    * `id(self.attr)` when `self.attr` is modified; this can be used to check for some particular conditions or modify other variables::

        instance=SomeClass()  # calls instance.postLoad(None)
        instance.aF_trigger=3 # calls instance.postLoad('aF_trigger')
    
      .. note:: Pay attention to not call `postLoad` in infinite regression. 

    Python classes may be further derived from in python, along those lines::

        class SomeChild(SomeClass): # python base class only
            _PAT=woo.pyderived.PyAttrTrait
            _attrTraits=[
                _PAT(float,'extraAttr',1.,triggerPostLoad=True,doc='Attributes as usual; postLoad is supported.'),
            ]
            def postLoad(self,I):
                if I=='extraAttr': pass
                # don't forget to eventually call parent's class postLoad, if you define postLoad in the derived class
                # otherwise the triggers from the parents class would not work
                else: super(SomeChild,self).postLoad(I)
            # newer pickling (pybind11)
            def __new__(klass,**kw):
                self=super().__new__(klass)
                self.wooPyInit(SomeChild,SomeClass,**kw) # this class, parent class, keywords
                return self
            # older pickling (boost::python)
            def __init__(self,**kw):
                SomeClass.__init__(self) # default-construct the parent
                self.wooPyInit(SomeChild,SomeClass,**kw) # this class, parent class, keywords
    
    Derived classes should suppor pickling, GUI, documentation, type-checking, postLoad just like python class deriving from c++ directly. The internal machinery is checked by :obj:`woo.tests.core.TestPyDerived`.

    '''
    def wooPyInit(self,derivedClass,cxxBaseClass,**kw):
        '''Inject methods into derivedClass, so that it behaves like woo.core.Object,
        for the purposes of the GUI and expression dumps'''
        cxxBaseClass.__init__(self) # repeat, just to make sure
        # this class does not derive from c++ directly, call the helper that one for it as well (recurses)
        if hasattr(cxxBaseClass,'wooPyInit'):
            # print 'Calling python base class wooPyInit'
            self.wooPyInit(cxxBaseClass,cxxBaseClass.__base__)
        self.cxxBaseClass=cxxBaseClass
        self.derivedClass=derivedClass
        # print derivedClass.__name__,'wooPyInit'
        # initialize these conditionally; when the base class is in python, it has already set those
        if not hasattr(self,'_instanceTraits'): self._instanceTraits={}
        if not hasattr(self,'_attrValues'): self._attrValues={}
        if not hasattr(self,'_attrTraitsDict'): self._attrTraitsDict={}
        self._attrTraitsDict.update(dict([(trait.name,trait) for trait in derivedClass._attrTraits]))

        for trait in derivedClass._attrTraits:
            # basic getter/setter
            getter=(lambda self,trait=trait: self._attrValues[trait.name])
            setter=(lambda self,val,trait=trait: self._attrValues.__setitem__(trait.name,trait.coerceValue(val)))
            if trait.triggerPostLoad:
                if not hasattr(derivedClass,'postLoad'): raise RuntimeError('%s.%s declared with triggerPostLoad, but %s.postLoad is not defined.'%(derivedClass.__name__,trait.name,derivedClass.__name__))
                def triggerSetter(self,val,trait=trait):
                    self._attrValues[trait.name]=trait.coerceValue(val)
                    self.postLoad(trait.name)
                setter=triggerSetter
            # chain validation and actual setting
            def validatingSetter(self,val,trait=trait,setter=setter):
                trait.validate(val)
                setter(self,val)
            # deprecated attribute: raise error on any access
            def accessError(self,_val=None,trait=trait): raise ValueError('Error accessing %s.%s: '+trait.doc)
            if trait.deprecated: getter=validatingSetter=accessError
            setattr(derivedClass,trait.name,property(getter,validatingSetter,None,trait.doc))
            self._attrValues[trait.name]=trait.ini
        # print derivedClass.__name__,self._attrValues
        if kw:
            for k in kw:
                if not hasattr(self,k): raise AttributeError('No such attribute: %s'%k)
                if k in self._attrValues: self._attrValues[k]=self._attrTraitsDict[k].coerceValue(kw[k])
                else: setattr(self,k,kw[k])
        derivedClass.__str__=lambda o:'<%s @ %d (py)>'%(derivedClass.__name__,id(o))
        derivedClass.__repr__=derivedClass.__str__
        derivedClass._cxxAddr=property(lambda sefl: id(self))
        # pickle support
        def __getstate__(self):
            #print '__getstate__ in python'
            ret=self._attrValues.copy()
            ret.update(cxxBaseClass.__getstate__(self)) # get boost::python stuff as well
            return ret
        def __setstate__(self,st):
            #print '__setstate__ in python'
            # set managed attributes indirectly, to avoid side-effects
            for k in list(st.keys()):
                if k in self._attrValues:
                    self._attrValues[k]=self._attrTraitsDict[k].coerceValue(st.pop(k))
            # set remaining attributes using setattr
            for k,v in st.items(): setattr(self,k,v)
            # call postLoad as if after loading
            if hasattr(derivedClass,'postLoad'): self.postLoad(None)
        def deepcopy(self,**kw):
            '''The c++ dedepcopy uses boost::serialization, we need to use pickle. As long as deepcopy
            is called from python, this function gets precedence over the c++ one. Additional keyword parameters are used to immediately set parameters on the copy before returning.'''
            import pickle
            copy=pickle.loads(pickle.dumps(self))
            for k in kw: setattr(copy,k,kw[k])
            return copy
        def save_error(self,out):
            raise IOError('%s.save not allowed for Python classes, use %s.dump instead (only attributes of the closest c++ base class would be saved with save with boost::serialization, losing all python-only data).'%(derivedClass.__name__,derivedClass.__name__,))
        derivedClass.__getstate__=__getstate__
        derivedClass.__setstate__=__setstate__
        derivedClass.deepcopy=deepcopy
        derivedClass.save=save_error
        if hasattr(derivedClass,'postLoad'):
            # print derivedClass.__name__,': will call postLoad at construction time; attrValues are',str(self._attrValues)
            derivedClass.postLoad(self,None)
        


if __name__=='wooMain':
    # do not define this class when running woo normally,
    # so that it does not show up in the preprocessor dialogue
    
    # inheritance order must not change, due to us using __bases__[0] frequently
    # when traversing the class hierarchy
    class SamplePyDerivedPreprocessor(Preprocessor,PyWooObject):
        'Sample preprocessor written in pure python'
        _classTraits=None
        _attrTraits=[
            PyAttrTrait(bool,'switch',True,"Some bool switch, starting group",startGroup='General'),
            PyAttrTrait(int,'a',2,"Integer argument in python"),
            PyAttrTrait(str,'b','whatever',"String argument in python"),
            PyAttrTrait([Node,],'c',[],"List of nodes in python"),
            PyAttrTrait(float,'d',.5,"Parameter with range",range=Vector2(0,.7),startGroup='Advanced'),
            PyAttrTrait(int,'choice',2,"Param with choice",choice=[(0,'choice0'),(1,'choice1'),(2,'choice2')]),
            PyAttrTrait(int,'flags',1,"Param with bits",bits=['bit0','bit1','bit2','bit3','bit4'],buttons=(['Clear flags','self.flags=0','Set flags to zero'],True)),
            PyAttrTrait(int,'choice2',2,'Param with unnamed choice',choice=[0,1,2,3,4,5,6,-1]),
            PyAttrTrait(Vector3,'color',Vector3(.2,.2,.2),"Color parameter",rgbColor=True),
            PyAttrTrait(float,'length',1.5e-3,"Length",unit='mm'),
            PyAttrTrait(str,'outDir','/tmp',dirname=True,doc='output directory'),
        ]
        def __init__(self,**kw):
            # construct all instance attributes
            Preprocessor.__init__(self)
            self.wooPyInit(SamplePyDerivedPreprocessor,Preprocessor,**kw)
        def __call__(self):
            import woo.core, woo.dem, woo.utils
            S=woo.core.Scene(fields=[woo.dem.DemField()])
            S.dem.par.add(Wall.make(0,axis=2,sense=1),nodes=False)
            S.dem.par.add(Sphere.make((0,0,1),radius=.2),nodes=True)
            S.dem.gravity=(0,0,-10)
            S.dt=1e-4*woo.utils.pWaveDt(S)
            S.engines=woo.dem.DemField.minimalEngines(damping=.01)
            return S

    import woo.pre
    woo.pre.SamplePyDerivedPreprocessor=SamplePyDerivedPreprocessor

    t=PyAttrTrait(str,'sChoice','aa',choice=['aa','bb','cc'],doc='string choice with validation')
    t.validate('abc')



